This invention relates to aircraft air-conditioning systems and, more particularly, to apparatus and method of cooling the passenger cabins of parked aircraft.
A number of systems have been developed over the years to satisty the requirement of maintaining the temperature of the passenger cabin of modern day aircraft at a level comfortable to the passengers during the time aircraft is parked. In such aircraft, the high density of passengers, the interior lighting, the large number of windows, and the heavily insulated fuselage all contribute to raising the temperature of the cabin of the parked aircraft to uncomfortable levels. Accordingly, it has been found necessary to provide a cooling system to lower the aircraft cabin temperature, even when the aircraft is parked in locations with relatively cold outside ambient temperatures.
One type of prior art system for cooling the cabin of a parked aircraft utilizes an on-board auxiliary power unit which is generally a small, jet-fueled turbine. The turbine, which is operated when the aircraft is parked, is used to power the on-board cooling system. This same cooling system is powered by the main engines during flight.
Another type of prior art system for cooling the cabin of a park aircraft utilizes one or more on-board air cycle machines which are special-purpose heat pumps. These machines cool the cabin air when they are supplied with a source of high-pressure, high temperature air. During flight, the source of air is an on-board compressor driven by the main engines. When the aircraft is parked, a ground-based air compressor is connected to the airplane to drive the heat pumps. This connection is made using a hose which links the compressor to a heat pump connector provided on the outer surface of the aircraft fuselage.
Yet another type of system for cooling the cabin of a parked aircraft utilizes a ground-based air conditioner unit which provides cool air under pressure directly into the cabin air-conditioning duct system. This ground-based air conditioner, which may be fixed in location or portable, is connected to the parked airplane using a flexible hose. This hose links the air conditioner to a connector, provided on the exterior of the fuselage, which communicates directly with the cabin ducts. In this mechanization, there is no need to operate the on-board cooling system when the aircraft is parked.
Of the previously described types of cooling system, the ground-based air conditioner unit is generally recognized as being the most energy efficient. Typically, prior art ground-based air conditioner units require from one-fifth to one-tenth the energy of those systems employing on-board auxiliary power units, and from one-half to one-fourth the energy of those systems employing on-board air cycle machines.
Even though ground-based air conditioner systems are generally more efficient than many other types of cooling systems, they still require large amounts of power for their operation. For example, electrically operated air conditioner systems for large commercial jet aircraft may require in excess of three hundred and fifty kilowatts of power for their operation.
Further, prior art ground-based air conditioner systems typically employ very large and powerful blowers in order to generate sufficient air flow to maintain the desired cabin temperature. These blowers, some of which may be rated in excess of one hundred and fifty brake horsepower, generate substantial levels of noise adjacent the air conditioner unit. In addition, these large blowers cause the cool air to exit the cabin air ducts at sufficiently high velocities to produce noticeable cabin noise.
Yet another drawback to prior art ground-based air conditioner systems is the high moisture content of the cool air delivered to the cabin air ducts. This moisture increases cabin humidity, causing mist formation and contributing to passenger discomfort.
Accordingly, it is an object of the present invention to provide new and improved apparatus and methods for cooling the cabins of parked aircraft.
It is another object of the present invention to reduce the power consumption of ground-based aircraft air conditioning systems.
It is yet another object of the present invention to improve the cabin environment of parked aircraft by reducing the noise and humidity produced by the air conditioning system.